Anisotropy coefficient in 2d polydisperse model of composite structures

The article presents a mathematical model describing the coefficients related to the electrical conductivity of the varistor. Varistor’s conductivity is closely related to its microstructure, which consists of ZnO grains surrounded by an amorphous bismuth oxide layer, in- tergrain areas rich in reaction products between the varistor components, and pores. Only active grain boundaries take part in the current conduction process, which are mainly ZnO grains surrounded by amor- phous bismuth oxide. The intergranular areas and pores are electrically inactive, i.e. unnecessary from the point of view of conducting electric current. The angle θ determined from the mathematical model in- dicates the direction of current flow in the varistor, which occur the largest number of active grain bound- aries. The direction perpendicular to θ indicates the presence of the largest number of electrically inactive areas. Having knowledge about the most optimal di- rection of current flow in the varistor can influence the improvement the performance of the varistor and thereby its electroprotection.